Question

I have a table customers where each cust has UserID as “A000” now I need to get the last entered ID from the database and display it in my textbox.

Can anyone suggest me how do I do this?

As I have seen many articles describing about

SELECT @@IDENTITY
SELECT SCOPE_IDENTITY()
SELECT IDENT_CURRENT('TableName')

but unable to know where to use it correctly.

And here is how I’m doing it :

 Dim strConnection As String = "Data Source=.\SqlExpress;Initial Catalog=Subscription;Integrated Security=True"
 'Establish SQL Connection
 Dim con As New SqlConnection(strConnection)
 'Open database connection to connect to SQL Server
 con.Open()
 'Data table is used to bind the resultant data
 Dim dtusers As New DataTable()
 'Create a new data adapter based on the specified query.
 Dim da As New SqlDataAdapter("SELECT MAX(UserID) FROM Customers", con)
 Dim cmd As New SqlCommandBuilder(da)
 da.Fill(dtusers)
 con.Close()

Answer 1

Use ExecuteScalar :

Dim comm as new SqlCommand
comm.CommandText = "SELECT MAX(UserID) FROM Customers"
comm.Connection = con

Dim MaxUserID as object = comm.ExecuteScalar()

Use the ExecuteScalar method to retrieve a single value (for example,
an aggregate value) from a database

Side Note : ExecuteScalar() may return a null reference (Nothing in VB.NET) if the result of the command is empty like when there are no records in the table or there is condition that doesn’t produce any records. Make sure you check that before assigning the value to your TextBox.